WO2008061185A1 - Manipulation d'écoulement dans des écoulements biologiques utilisant des générateurs de tourbillons - Google Patents

Manipulation d'écoulement dans des écoulements biologiques utilisant des générateurs de tourbillons Download PDF

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Publication number
WO2008061185A1
WO2008061185A1 PCT/US2007/084816 US2007084816W WO2008061185A1 WO 2008061185 A1 WO2008061185 A1 WO 2008061185A1 US 2007084816 W US2007084816 W US 2007084816W WO 2008061185 A1 WO2008061185 A1 WO 2008061185A1
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Prior art keywords
flow
blood
projections
induce
boundary layer
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PCT/US2007/084816
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English (en)
Inventor
Ari Glezer
Ajit P. Yoganathan
Lakshmi P. Dasi
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Georgia Tech Research Corporation
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Application filed by Georgia Tech Research Corporation filed Critical Georgia Tech Research Corporation
Priority to EP07864458A priority Critical patent/EP2086469A1/fr
Publication of WO2008061185A1 publication Critical patent/WO2008061185A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
    • A61M1/36—Other treatment of blood in a by-pass of the natural circulatory system, e.g. temperature adaptation, irradiation ; Extra-corporeal blood circuits
    • A61M1/3672—Means preventing coagulation
    • A61M1/3675—Deactivation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/0077—Special surfaces of prostheses, e.g. for improving ingrowth
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/24—Heart valves ; Vascular valves, e.g. venous valves; Heart implants, e.g. passive devices for improving the function of the native valve or the heart muscle; Transmyocardial revascularisation [TMR] devices; Valves implantable in the body
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/0077—Special surfaces of prostheses, e.g. for improving ingrowth
    • A61F2002/0081—Special surfaces of prostheses, e.g. for improving ingrowth directly machined on the prosthetic surface, e.g. holes, grooves
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/04—Hollow or tubular parts of organs, e.g. bladders, tracheae, bronchi or bile ducts
    • A61F2/06—Blood vessels
    • A61F2002/068—Modifying the blood flow model, e.g. by diffuser or deflector

Definitions

  • the present invention relates to systems and methods for manipulating biological flows. More particularly, the present invention relates to managing flow through medical devices to reduce risk of adverse events attributable to shear stress.
  • Shear stress can lead to coagulation and thromboemboli formation by either damaging the red blood cell (RBC) or by mechanically activating the platelet.
  • RBC red blood cell
  • High levels of shear stress can tear the RBC membrane, thus exposing tissue factor to the plasma and initiating the tissue factor pathway of the coagulation cascade.
  • Shear stress can also trigger the coagulation cascade by activating platelets directly. Platelets are activated by shear stress that results in mechanotransduction of the force to a GPIb receptor.
  • This mechanotransduction enables binding of the GPIb receptor to Von Willebrand Factor (vWF) and a subsequent influx of calcium ions, resulting in platelet activation.
  • vWF Von Willebrand Factor
  • the GpIIb/IIIa receptor is activated and can then bind to other ligands such as fibrinogen, vWF, fibronectin, and vitronectin.
  • the coagulation cascade is propagated and can lead to the formation of thrombin-anti- thrombin III (TAT), which is a relative measure of thrombin formation.
  • TAT thrombin-anti- thrombin III
  • RBCs are vulnerable to sub-lethal damage at shear stresses of 500 dynes/cm 2 and by as little as 10-100 dynes/cm 2 in the presence of foreign surfaces.
  • platelet activation can occur at shear stresses as low as 60-80 dynes/cm .
  • the flow control devices should counteract the formation of strong vortices thereby reducing the overall platelet activation potential of cardiovascular devices.
  • the flow control devices should mitigate the adverse effects of high shear stress in blood-contacting devices and manipulate secondary vorticity concentrations within the blood flow.
  • the flow control devices should enhance cross stream mixing and momentum transfer to diminish local velocity gradients and corresponding shear stress distributions.
  • the present application discloses various devices for use in combination with a fluid flow having a biologic component and subject to an adverse response to shear stress.
  • the device includes a surface in contact with the flow of the fluid.
  • the surface has a longitudinal direction extending from a leading end toward a trailing end and aligned with a direction of the flow.
  • the device is susceptible to fluid flow phenomena including boundary layer formation within the flow sufficient for a resulting shear stress to induce the thrombogenic response, or free shear flow formation such as jet, separation zones of sufficient characteristic to induce the thrombogenic response.
  • the surface includes a surface feature sufficient to alter the fluid flow such as to reduce the overall shear stress that the biologic components may encounter while transiting through the device.
  • aspects of the present invention include an implant for chronic placement in a patient's body.
  • the implant has a lumen defining a blood flow path for a blood flow having flow characteristics including a flow rate.
  • the implant has a surface at least partially defining the lumen and in contact with the blood flow.
  • the surface has a longitudinal direction extending from a leading end toward a trailing end.
  • the device is susceptible to fluid flow phenomena including boundary layer formation within the flow sufficient for a resulting shear stress to induce the response, or free shear flow formation such as jet, separation zones of sufficient characteristic to induce the thrombogenic response.
  • the surface includes a surface feature sufficient to alter the fluid flow such as to reduce the overall shear stress that the blood may encounter while transiting through the device.
  • the present invention includes examples of a device for receiving blood from a patient, treating the blood and returning the treated blood to the patient.
  • the device comprises a plurality of blood flow pathways for containing and directing a blood flow.
  • the blood flow has flow characteristics including a flow rate.
  • At least one of said pathways has a surface at least partially defining the pathway and in contact with the blood flow.
  • the surface has a longitudinal direction extending from a leading end toward a trailing end and the surface is susceptible to inducing boundary layer formation, jet formation, or flow separation within the blood flow.
  • the surface has characteristics sufficient to induce a thrombogenic response.
  • the surface includes a surface feature sufficient to alter the blood flow such as to reduce the overall shear stress that the blood may encounter while transiting through the device.
  • FIG. 1 is a schematic representation of a prior art device having surfaces in chronic contact with a patient's blood flow and having no passive means for reducing shear stress in the flow;
  • FIG. 2 is a schematic representation of the device of FIG. 1 modified according to the present invention.
  • FIG. 3 is the view of FIG. 2 illustrating flow response to the modification of the present invention
  • FIGs. 4 and 4A depict planer protuberances consistent with embodiments of the invention
  • FIG. 5 depicts hemispherical protuberances consistent with embodiments of the invention.
  • FIG.6 depicts maps of instantaneous vorticity fields at the moment of valve closure;
  • FIG. 7 depict contour plots of mean velocity for the steady b-datum jet from the valve without and with rectangular vortex generators and Reynolds shear stress for the steady b-datum jet from the valve without and with rectangular vortex generators;
  • FIG.8 depicts comparison of TAT concentration with and without vortex generators
  • FIG.9 depicts shows a situation where embodiments of the present invention may be employed on a device external to a patient
  • FIG. 10 depicts a situation where embodiments of the present invention may be deployed on a device internal to the patient;
  • FIG. 11 depicts a bileaflet heart valve experiencing leakage
  • FIG. 12 depicts a bileaflet heart valve having flexible tips.
  • the present invention will be described in a preferred embodiment of passive surface modifications to avoid excessive shear stress in devices in contact with blood flow.
  • Such devices may be chronically implanted devices (e.g., LVAD's, stents, valves, etc.) or may be external devices (e.g., blood pumps, blood oxygenators, etc.) or may be blood conduits (e.g., catheters).
  • LVAD's, stents, valves, etc. may be external devices (e.g., blood pumps, blood oxygenators, etc.) or may be blood conduits (e.g., catheters).
  • blood conduits e.g., catheters
  • the present invention is applicable to biological fluids in general (including therapeutic fluids such as therapeutic agents such as cell components, drugs or the like administered in an aqueous medium).
  • FIG. 1 illustrates a prior art device 100 with a surface in contact with a patient's blood flow.
  • the device 100 includes walls 102 and 104.
  • a bulk flow 126 contacts the device 100 at the leading edges 102a, 104a of walls 102 and 104.
  • boundary layers 122 and 124 may form in the entrance region of the device 100.
  • L length
  • D diameter
  • Boundary layers 122 and 124 cause shear stresses to develop along walls 102 and 104.
  • FIGs. 2 and 3 a schematic representation of a device 300 according to various aspects of the present invention is shown.
  • Device 300 includes surfaces 302 and 304 having various vortex generators 206, 208, and 110 spaced from leading edges 302a and 304a along a flow direction (indicated by the arrows in FIG. 3). Note that while FIGs. 2 and 3 show three different types of vortex generators depicted on surfaces 302 and 304 it is contemplated that a single type of vortex generator or two or more vortex generators may be implemented on device 300.
  • Vortex generators 306, 308, and 310 may be characterized by characteristics including but not limited to angle of attack, height, depth, flexibility, and spacing sufficient to create a region of vortex formation proximate vortex generators 306, 308, and 310. It will be appreciated that selection of such characteristics for a given flow characteristic (such as flow rate) is well within the skill level of one of ordinary skill in the art having the benefit of the present disclosure.
  • Vortex generators 306, 308, and 310 may induce the formation of secondary counter-rotating streamwise vortex pairs 314 which interact with the shear layer and induce cross stream mixing. This cross-stream mixing leads to broadening of the jet stream and to dissipation of small-scale motions.
  • vortex generators such as vortex generators 310 may be conformable.
  • conformable flow control elements stems from the fact that they may be designed to adapt their functionality to the cyclical state of the embedding flow during a cardiac cycle.
  • vortex generators that are highly effective for reducing blood damage during valve closure may be pushed out of the way (e.g., bend towards the surface) when the embedding flow reverses its direction to minimize losses.
  • the flexible flow control devices may be reconfigured and have different functionality to beneficially affect the reverse.
  • the functionality of the passive devices can be potentially enhanced by allowing them to interactively oscillate as they shed streamwise vorticity.
  • FIG. 12 shows an implementation of flexible tip passive flow control on the contemporary rigid bileaflet heart valve 1200 comprising flexible tips 1202 and leaflets 1204 and 1206.
  • Flexible tips 1202 help ensure smooth closing of heart valve 1200 thus eliminating the typical colliding nature of leaflets 1204 and 1206 closure. The closure has been attributed to formation of extreme pressure gradients that lead to cavitation and hemolysis. Flexible tips 1202 help ensure that the added compliance at the contact points provide a smooth contact as well as a damping effect to eliminate the water hammer effect. Additionally, it is anticipated that flexible tips 1202 may greatly reduce leakage through a b-datum and peripheral gaps during a cardiac cycle's leakage phase.
  • Protuberance or other surface irregularities may be rigid flow control elements.
  • protuberance or other surface irregularities may be flexible passive flow control elements.
  • the use of flexible elements for flow control is attractive because it offers expanded control authority.
  • the interest in conformable flow control elements stems from the fact that they can be designed to adapt their functionality to the cyclical state of the embedding flow during a flow cycle. For example, vortex generators that are highly effective for reducing blood damage during valve closure can be pushed out of the way (e.g., bend towards the surface) when the embedding flow reverses its direction to minimize losses.
  • the flexible flow control devices can be reconfigured and have different functionality to beneficially affect the reverse.
  • the functionality of the passive devices can be potentially enhanced by allowing them to interactively oscillate as they shed streamwise vorticity.
  • vortex generators 306, 308, and 310 are great enough to retard boundary layer formation thereby reducing shear stress at surfaces 302 and 304.
  • the internal blood flow within device 300 is shown at 326' and the approaching flow is shown at 326.
  • the height and spacing of vortex generators 306, 308, and 310 are small enough to discourage flow stagnation (e.g. pooling, clotting, and clumping of the flow) proximate vortex generators 306, 308, and 310.
  • flow stagnation e.g. pooling, clotting, and clumping of the flow
  • vortex generators 306, 308, and 310 can be at arbitrary angles to surfaces 302 and 304 and the flow.
  • the angle relative to surfaces 302 and 304 may be device specific.
  • the height and spacing of vortex generators 306 and 310 are such that vortex generators 306 and 310 do not substantially reduce a cross-sectional area in the flow direction or volumetric flow rate through device 300. Characterization of a substantial reduction in the cross-sectional area or volumetric flow rate may be a noticeable reduction in blood flow to the point that the effective diameter or other characteristic length associated with measuring the cross-sectional area or volumetric flow rate is reduced. For example, if vortex generators 306 and 310 reduce the cross-sectional area by 10-15%, this may constitute a substantial reduction in the cross-sectional area. Another example me be that if vortex generators 306 and 310 reduce the volumetric flow rate to the point vortex generators 306 and 310 simulate coronary artery plaque or other artery blockage, this may constitute a substantial reduction in the volumetric flow rate.
  • embodiments of the present invention utilize passive flow control devices for manipulating and controlling the evolution of both free and wall-bounded turbulent shear flows.
  • Passive flow control devices may have morphology and structural features to alter the flow over the device's surface and active flow control (e.g., movable fins or other movable protuberances) to achieve drag reduction, thrust production, and propulsive efficiency.
  • active flow control e.g., movable fins or other movable protuberances
  • These devices generally use distributed element arrays (e.g. surface irregularities) that may protrude above the surface or indentations or grooves that penetrate into the device's surface.
  • Vortex generators that protrude from the surface may include transverse cylinders, plates, and airfoils that may be oriented parallel or normal to the flow and within the boundary layer or shear layer or any other location where there is fairly strong shear within the flow.
  • these plates or airfoils may shed transverse (i.e. spanwise) vortices along the device and may lead to the wall boundary layer prematurely transitioning to turbulent flow (i.e. boundary layer "tripping"), turbulent flow structure modification, or may break up larger vortical eddies that are present in the flow.
  • the plates or airfoils i.e. surface irregularity
  • a heart valve 1100 may comprises leaflets 1102 and 1104. As a flow 1106 flows through heart valve 1100, the can be hinge leakage 1108 and leakage jet 1110 formation.
  • Vortex generators Low-aspect ratio (i.e., short span) plates and airfoils that are mounted normal to the surface along their (long) chords are called vortex generators. Because the vortex generators are mounted at an angle of attack relative to the oncoming flow, they form either clockwise or counterclockwise (depending on their orientation) "wing tip" streamwise vortices.
  • the vortex generators are typically arranged in spanwise arrays that can be formed with single (same orientation) or symmetric pairs to produce either single-sign or counter rotating streamwise vortex pairs.
  • Vortices scale with the characteristic dimensions of the generating elements and lead to enhancement of entrainment (e.g., transfer of high-momentum fluid towards the surface) and small-scale fluid mixing within the embedding flow field.
  • entrainment e.g., transfer of high-momentum fluid towards the surface
  • small-scale fluid mixing within the embedding flow field In external and internal flows, flow separation suppression or mitigation and mixing enhancement within free shear flows are typically dominated by large coherent vortical structures.
  • Flow control devices that are embedded in the flow surface include dimples, riblets, and small-scale streamwise grooves that can reduce turbulent skin friction. These riblets break up spanwise vortices and reduce the surface shear stress and momentum loss by preventing eddies from transporting high speed fluid close to the surface.
  • Free turbulent jets demonstrate that the interaction between the jet's predominantly azimuthal vorticity and the streamwise vortices induced by passive vortex generators can lead to mixing enhancement and therefore to reduction in shear. Moreover, the increase in small-scale motion within the flow leads to enhancement and consequently to dissipation of turbulent fluctuations.
  • Axial vorticity may be introduced by placing tabs at the jet exit such that they protruded into the flow with an area blockage of approximately 1-2% per tab. As little as two tabs may significantly increase mixing sufficiently to reduce the potential core length and increase the decay of the centerline velocity. This increased mixing and decay may increase jet spreading and reduce the flow shear.
  • Streamwise vorticity generation at the jet exit may be promoted by enforcing azimuthal excitation through vortex generators or tabs at the edge of the nozzle or by using corrugated, lobed, or indented nozzle edges.
  • surface irregularities or vortex generators may be placed in any type of device used to transport biological materials or materials susceptible to damage where there may be increased shear levels that may lead to damage due to flow separation internally or bifurcation within the device.
  • vortex generators may be used in cardiovascular device to reduce shear levels that may lead to blood damaged due to flow separation or bifurcation within blood vessels. The flow separation and bifurcation may cause separation and recirculation that may also lead to damage of the flow material.
  • the passive vortex generators may be fabricated using molding technologies and bio-compatible polymeric materials (e.g., PDMS). As noted above, the elasticity and other mechanical properties of the molding material may be selected so that the fins can bend appreciably (and therefore minimize their cross stream protrusion) when the flow over the leaflets reversed direction.
  • PDMS polymeric materials
  • Passive flow control devices can be effectively realized using advanced fabrication technologies.
  • soft polymers e.g., PDMS
  • PDMS polymers
  • rapid prototyping e.g. solid object printing
  • soft lithography e.g., lithography
  • these elastomers can be fabricated in submicron features with no discernible pattern degradation or surface distortion.
  • Submicron resolution molds can be generated by electron beam lithography, for example, to yield nano- scale patterns in replica molded elastomers.
  • the effectiveness of surface integrable flow control devices may facilitate their implementation using new, nano-and micro- fabrication technologies may allow custom-fitting these devices to specific patients.
  • vortex generators 206 and 210 may be substantially planer (FIG. 4), substantially hemispherical (FIG. 5), a combination of substantially planer and substantially hemispherical shapes, serrated edges either in or normal to the plane of the leaflet, etc.
  • Planar protuberances e.g. rectangular vortex generators
  • Each fin may produce a streamwise (wingtip) vortex where the sense of the vorticity (i.e., clockwise or counter clockwise) may depend on the angle of the fins 402 relative to a free stream.
  • each fin 402 may be 1 mm high (a base 0.5 mm thick) and may have an angle of attack of ⁇ 15° degrees relative to an oncoming flow.
  • protuberance may be based on an array of staggered hemispherical protuberances 502.
  • hemispherical protuberances 502 may have a diameter of 1 mm with an edge to edge spacing of 0.5 mm.
  • FIGs. 4 and 5 show the protuberances substantially parallel (FIG. 4) and substantially perpendicular (FIG. 5) to the blood flow direction, it is contemplated that the protuberances may be parallel, perpendicular, or a combination of both to blood flow direction.
  • FIG. 6 depicts maps of instantaneous vorticity fields at the moment of valve closure.
  • the flow characteristics of the transitory jet and the influence of vortex generators were investigated using high resolution particle image velocimetry (PIV).
  • the plane of measurement was aligned along the centerplane of the chamber and perpendicular to the leaflet axis.
  • the measurements were phase locked such that the velocity field was captured throughout the cardiac cycle of 860 ms with 20 ms increments.
  • the vorticity fields capture regurgitant jets for a heart valve having no vortex generators, rectangular or planer vortex generators, and hemispherical vortex generator.
  • TAT is an established measure to access the pro- coagulant potential of various valves.
  • a series of measurements were conducted in vitro. Heart valves with and without vortex generators were tested in a flow loop to measure the TAT concentration in blood over a period of one hour at 15 min intervals.
  • FIG. 8 depicts a comparison of TAT measurements (taken at 15 min intervals) in the three configurations considered here (i.e. the baseline valve, and in the presence of rectangular and hemispherical vortex generators).
  • This data clearly show that TAT concentration increases steadily with time for all three cases indicating a gradual progress in overall blood coagulation levels in the system.
  • the total TAT concentration in the presence of the vortex generators is substantially lower than in the baseline valve.
  • the presence of the rectangular vortex generators leads to a 42% decrease in TAT concentration compared to the baseline.
  • the production rate with the hemispherical vortex generators is higher than with the rectangular generators, but still significantly lower than in the absence of passive flow control (baseline).
  • the significance of these results is underscored by the fact that they actually provide conservative estimates of the reduction in blood damage and that in reality these effects may be considerably higher. This is due to background blood damage and activation that are caused by other components in the loop such as the pump, loop fittings etc.
  • Embodiments of the present invention may be utilized on mechanical heart valves and other replacement cardiovascular devices that are rigid.
  • embodiments of the present invention may be utilized on replacement cardiovascular devices and other devices in chronic contact with blood flow that are flexible and mimic real physiological heart valves, arteries, and physiological structures.
  • flexible elements e.g. surface edges and vortex generators
  • for cardiovascular flow control offers expanded control authority coupled with advanced, batch fabrication technologies.
  • a device may integrate a flexible material with hard/rigid materials during manufacturing to create soft tips at the edges to eliminate the clicking noise commonly associated with purely metallic heart valves.
  • the edges of hear valve leaflets may be a flexible material, (i.e. a quiet material) and a majority of the leaflet surface could be rigid (See FIG. 12).
  • vortex generators may be molded into soft and rigid materials. Molding the vortex generators into the materials may eliminate the need to separately glue them onto the surface.
  • an implantable medical device could be molded out of flexible materials like PDMS.
  • PDMS elastomer can conform to extremely small (submicron) features with no discernible pattern degradation or surface distortion.
  • these fabrication technologies suggest themselves as viable vehicles for realizing passive flow control devices in cardiovascular systems because soft polymers such as PDMS are stable, non-toxic, low-cost, with appealing physical and chemical properties that are also bio- and micro-fabrication compatible.
  • some of these materials can be selected to have desirable properties such as optical transparency, tunable surface chemistry, thermal stability, good bonding characteristics, elasticity, high-gas, and low-water permeability.
  • a patient is measured for a prosthetic device and after manufacturing, the device is implanted. This can lead to problems in that the measurements may be taken via ultrasound technology and at best are estimates of the size needs.
  • Many biocompatible materials can be molded quickly allowing for cardiovascular devices to be manufactured using rapid prototyping technologies.
  • rapid prototyping technologies and a surgeon may, in real time, manufacture a replacement cardiovascular device while the patient is on the operating table. For instance, after opening the patient's chest cavity the surgeon may measure the patient's heart directly. Once the direct measurements are taken, the actual machines necessary to manufacture a device (e.g. heart valve, replacement artery, stent) may be in the operating room and the replacement device fabricated in real time using direct measurements, not ultra sound measurements.
  • a device e.g. heart valve, replacement artery, stent
  • the passive vortex generators may be fabricated using molding technologies and biocompatible polymeric materials (e.g., PDMS).
  • An aspect of the flexible vortex generators is the ability to prescribe the mechanical properties of the material and therefore the relaxation time following the change in flow direction.
  • the relaxation time can be scaled to optimize performance such that the vortex generators are fully extended only when the transitory jet reaches its full speed (i.e., before the valve closes completely).
  • FIG. 9 schematically illustrates the present invention employed on a device 902 external to a patient 904.
  • FIG. 9 shows device 902 connected to patient 904 via conduits 906 and 908.
  • Any number of components within device 902 may be fitted with vortex generators in efforts to minimize damage to biological fluids.
  • device 902 may be a blood pump used during heart surgery. Piping within device 902 may be fitted with vortex generators as well as facets of other internal components.
  • conduits 906 and 908 may also be fitted with vortex generators to minimize damage to biological fluids.
  • device 902 may include: blood pumps, blood oxygenators, dialysis machines, drug delivery machines, syringes, etc.
  • device 902 may only receive biological fluids from patient 904.
  • device 902 may be any device used by agencies such as the RED CROSS during blood drives, or devices used by physicians do collect biological samples such as tissue and urine from patients.
  • device 902 may only supply biological fluids to patient 904.
  • device 902 may be a device used during chemotherapy to deliver cells, drugs, blood, or other medical and biological elements to patient 904.
  • FIG. 10 shows the present invention employed on a device 1002 internal to a patient 1004.
  • FIG. 10 shows device 1002 implanted into patient 1004.
  • device 1002 may be a stent used to prop open an artery and the stent's facets may be fitted with surface protrusions and surface indentations to minimize damage to blood flowing though the stent.
  • device 1002 may include heart valves, stents, LVAD 's, etc.
  • vortex generators may be utilized in systems where flow through the system may experience a discontinuity (e.g. between two different size pipes or tubes) giving rise to a velocity jump as the flow goes from the large diameter tube to a small diameter tube or vice versa.
  • a discontinuity e.g. between two different size pipes or tubes
  • Surface irregularities may be used to help mitigate the effects of any sudden changes in velocity.

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  • Health & Medical Sciences (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Public Health (AREA)
  • Biomedical Technology (AREA)
  • Veterinary Medicine (AREA)
  • Engineering & Computer Science (AREA)
  • Cardiology (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Oral & Maxillofacial Surgery (AREA)
  • Transplantation (AREA)
  • Anesthesiology (AREA)
  • Hematology (AREA)
  • External Artificial Organs (AREA)
  • Prostheses (AREA)
  • Closures For Containers (AREA)

Abstract

L'invention concerne un dispositif destiné à être utilisé en combinaison avec un écoulement de fluide ayant un composant biologique et soumis à une réponse adverse à une contrainte de cisaillement comprenant une surface en contact avec l'écoulement du fluide. La surface possède une direction longitudinale qui s'étend d'une extrémité avant vers une extrémité arrière et alignée avec une direction de l'écoulement. La surface est susceptible d'induire la formation de couches limites dans l'écoulement de manière suffisante afin qu'une contrainte de cisaillement résultante induise la réponse. La surface comprend une caractéristique de surface suffisante pour induire le déclenchement de couches limites dans l'écoulement afin de retarder la croissance de la formation de couches limites suivant la longueur.
PCT/US2007/084816 2006-11-15 2007-11-15 Manipulation d'écoulement dans des écoulements biologiques utilisant des générateurs de tourbillons WO2008061185A1 (fr)

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EP07864458A EP2086469A1 (fr) 2006-11-15 2007-11-15 Manipulation d'écoulement dans des écoulements biologiques utilisant des générateurs de tourbillons

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US86591906P 2006-11-15 2006-11-15
US60/865,919 2006-11-15

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WO2008061185A1 true WO2008061185A1 (fr) 2008-05-22

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WO2008119520A1 (fr) * 2007-03-30 2008-10-09 Acandis Gmbh & Co. Kg Implant, procédé et dispositif pour produire un implant de ce type
WO2013040544A2 (fr) * 2011-09-15 2013-03-21 Cornell University Implant biomédical destiné à être utilisé dans des environnements de contrainte de cisaillement de fluide
EP2967823A4 (fr) * 2013-03-13 2016-11-16 Palmaz Scient Inc Caractéristiques et motifs topographiques sur une surface d'un dispositif médical et leurs procédés de fabrication
WO2017024357A1 (fr) * 2015-08-13 2017-02-16 The Brain Protection Company PTY LTD Dispositifs d'amortissement implantables pour le traitement de la démence et systèmes et procédés d'utilisation associés
US11045297B2 (en) 2012-10-18 2021-06-29 Vactronix Scientific Llc Topographical features and patterns on a surface of a medical device and methods of making the same

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008119520A1 (fr) * 2007-03-30 2008-10-09 Acandis Gmbh & Co. Kg Implant, procédé et dispositif pour produire un implant de ce type
WO2013040544A2 (fr) * 2011-09-15 2013-03-21 Cornell University Implant biomédical destiné à être utilisé dans des environnements de contrainte de cisaillement de fluide
WO2013040544A3 (fr) * 2011-09-15 2013-05-10 Cornell University Implant biomédical destiné à être utilisé dans des environnements de contrainte de cisaillement de fluide
US9629713B2 (en) 2011-09-15 2017-04-25 Cornell University Biomedical implant for use in fluid shear stress environments
US11045297B2 (en) 2012-10-18 2021-06-29 Vactronix Scientific Llc Topographical features and patterns on a surface of a medical device and methods of making the same
EP2967823A4 (fr) * 2013-03-13 2016-11-16 Palmaz Scient Inc Caractéristiques et motifs topographiques sur une surface d'un dispositif médical et leurs procédés de fabrication
WO2017024357A1 (fr) * 2015-08-13 2017-02-16 The Brain Protection Company PTY LTD Dispositifs d'amortissement implantables pour le traitement de la démence et systèmes et procédés d'utilisation associés
US10064626B2 (en) 2015-08-13 2018-09-04 The Brain Protection Company PTY LTD Implantable damping devices for treating dementia and associated systems and methods of use
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US20080110881A1 (en) 2008-05-15
US20080121046A1 (en) 2008-05-29
US8834911B2 (en) 2014-09-16
EP2086469A1 (fr) 2009-08-12

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